December 2010

Standardized system for PMDs wins nod

The explosive growth in research and clinical applications for plantar pressure measurement devices (PMDs) has led to efforts to standardize protocols so that data can be more easily interpreted and compared by scientists and clinicians. The standardization project, spearheaded by Claudia Giacomozzi, PhD, senior researcher at the Italian National Institute of Health (ISS), has recently gained significant momentum. Giacomozzi hopes to have industry agreement to the ISS team’s recommendations within a few months.

“To have correct and reliable measurement, you have to have reliable instrumentation,” Giacomozzi explained. “You have to decide which parameters you want to measure and how you will calculate them. For example, different companies use different algorithms to calculate the pressure-time integral, which leads to trouble comparing results from different devices.”
In a recent paper, Giacomozzi noted that differences in sensor technology, matrix spatial resolution, pressure range, sampling rate, calibration procedures, and raw data processing lead to significant differences in the accuracy of PMDs. In patients with diabetic neuropathy, for example, she pointed out that clinicians use peak plantar pressure thresholds to assess the risk of ulceration. But discrepancies between systems in the measured pressure values contribute to confusion about the definition of such risk thresholds.

Generally, standardization would cover hardware performance, measuring protocols, data processing, and parameters related to diagnosis and therapy. Giacomozzi and her team also want regulation of PMDs as medical devices, international and intercorporate cooperation on standards, and simplification of terminology. Even the discipline itself is now referred to by a plethora of names: baropodometry, pedobarometry, and pedobarography. The team is pushing for adoption of the less convoluted “pedography” instead.

Giacomozzi and her ISS colleagues have so far compared five commercial PMDs with respect to criteria including sensor response variability; sensor hysteresis (a type of memory effect); sensor creep (variation of pressure response over time); and platform response in the accuracy and repeatability of center-of-pressure coordinates. Their results have led to recommendations to manufacturers in areas such as in-house technical assessment, calibration, documentation, and monitoring.

“I entirely agree with Dr. Giacomozzi about this,” said David Armstrong, DPM, MD, PhD, a professor of surgery at the University of Arizona College of Medicine. “One of the major goals of our research team over the past 15 to 20 years has been to create a diagnostic and therapeutic lingua franca. We have to be speaking the same language in different clinics around the world, and if we have to constantly do conversions it makes things more complicated. This is going to become even more important as we develop better algorithms to compare relative pressures, or to assess dynamic and static foot function.”

For Karen Nolan, PhD, an assistant professor in the department of physical medicine and rehabilitation at the University of Medicine and Dentistry of New Jersey, and a researcher at the Kessler Foundation in West Orange, NJ, solid reporting can help compensate for shortfalls in standardization.

“If we come up with a standard system of accurately reporting—from calibration to the selection of variables to the functionality of the equipment—then we can compare data,” she said. “It’s important that you know that a value or a piece of data you’re receiving from a test is accurate and usable, so you’re never wasting the subject’s time.”

Nolan believes that much of the potential of PMDs lies ahead, and that progress will be driven from the laboratory to the clinic.

“If you can’t get standards in research, it will never be implemented in the clinic,” she said. “MRI [scans] started out as research tools, but in order for them to be relied on clinically, they had to come up with accuracy criteria for all of the different machines. That’s where we’re coming from. For the industry, it’s a win-win, because when the standards get created, the technology becomes more widespread, more reliable, and better utilized.”